Phase change memory device with alternating adjacent conduction contacts and fabrication method thereof

ABSTRACT

A phase change memory device and an associated method of making same are presented. The phase change memory device, includes first wiring lines, second wiring lines, memory cells, and conduction contacts. The first wiring lines are arranged substantially in parallel to each other so that the first wiring lines are grouped into odd and even numbered first wiring lines. The memory cells are coupled to the first and second wiring lines. The conduction contacts coupled to the first wiring lines so that only one conduction contact is coupled to a center of a corresponding odd numbered first wiring line. Also only two corresponding conduction contacts are coupled to opposing edges of a corresponding even numbered first wiring line. Accordingly, the conduction contacts are arranged on the first wiring lines so that conduction contacts are not adjacent to each other with respect to immediately adjacent first wiring lines.

CROSS-REFERENCES TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. 119(a) to Koreanapplication number 10-2009-0048357, filed on Jun. 2, 2009, in the KoreanPatent Office, which is incorporated by reference in its entirety as ifset forth in full.

BACKGROUND

1. Technical Field

The embodiments described herein relate to a semiconductor memory deviceand, more particularly, to a phase-change memory device and a method formanufacturing the same.

2. Related Art

A phase change random access memory (PRAM) is regarded as a non-volatilememory device. PRAMs are manufactured using a phase-change materialwhich is capable of reversibly changing phases between an orderedcrystalline solid state phase and a disordered amorphous solid statephase as a function of temperature. PRAMs also provide a way of storinga set status or a reset status because their different solid statephases exhibit distinctly different resistance difference.

PRAM memory devices can be designed to be highly integrated. As aresult, word line resistances in highly integrated PRAMs increase.Recently, metal contacts can be configured to be arranged between thecell strings and metal word lines so that they are connected to themetal contacts which minimizes this problem of an increased resistanceof the word line.

FIG. 1 is a sectional view of a conventional PRAM. Referring to FIG. 1,diodes 107 are formed on a semiconductor substrate 101 which a junctionregion 103 as a word line is formed therein. Phase change materialpatterns 109 are formed on the diodes 107 to form respective unit memorycells. Top electrode contacts 113 and bit lines 117 are formed on thephase change material patterns 109. Herein, the reference numerals 105,115 and 119 designate a first though a third interlayer insulatinglayers, respectively.

Word line contacts 121 are arranged to be coupled to the junction region103 between adjacent cell strings 125 along every predetermined numberof cell strings 125. A metal word line 123 which is electricallyconnected, i.e., coupled, to the word line contacts 121 are arrangedvertically relative to the bit lines 117.

Typically, the word line contacts 121 are arranged every 8 unit memorycells. However, as the integration of a semiconductor memory deviceincreases, the diameter of the word line contact 121 decreases.Accordingly, it is difficult to ensure the desired CD (CriticalDimension) in patterning holes for the word line contacts 121.Furthermore, since the space between the patterns becomes narrower, thena bridge with the adjacent holes can occur and thereby reduces the yieldof the device.

FIG. 2 is a stylized lay out of the PRAM in FIG. 1. Referring to FIG. 2,the word line contacts 121 are shown arranged between every eight unitsof memory cells in the extension direction of the metal word line 123.

As the level of integration increases for semiconductor memory devices,it is becoming more difficult to ensure the desired CD. Also, as thedistance D1 between the adjacent word line contacts 121 increases,unwanted bridges can occur between adjacent word line contacts 121.Furthermore, misalignment is also more likely to occur in forming theword line contacts 121. Furthermore, it becomes more and more difficultto ensure the minimum requirements to prevent misalignments as a resultof downsizing the dimensional layout ratios of the device.

Furthermore, the process of forming contact holes with the two-layeredthrough four-layered stack structures is carried out so as to form theword line contact 121. Since the photo and exposure process for thecontact hole is carried out by using the high-cost apparatus, the costrequired to form the word line contacts 121 in these types of stackstructures which are arranged every 8 cell strings increases.Furthermore, when the diameter in the contact hole is reduced based onthe demands for more highly integrated devices, then gap filling is morelikely to be degraded which reduces the productivity of device.

SUMMARY

The inventive concept provides a phase change memory device and a methodfor manufacturing the same being capable of ensuring the margin betweenadjacent word line contacts.

The inventive concept also provides a phase change memory device and amethod for manufacturing the same being capable of sufficiently ensuringadequately sized diameters of word line contacts irregardless of anincrease in the downsizing ratio of the device.

According one embodiment provides a phase change memory device thatincludes a plurality of first wiring lines, a plurality of second wiringlines, a plurality of unit memory cells connected to the plurality offirst wiring lines and the plurality of second wiring lines, and aplurality of conduction contacts configured to be connected to the firstwiring lines every desired unit memory cell number, wherein theconduction contacts of the plurality of conduction contacts which arearranged on adjacent first wiring lines are configured not to bearranged adjacent to each other in a second wiring line direction.

Another example embodiment provides a phase change memory deviceincludes a plurality of junction type word lines configured to bearranged to be spaced apart in parallel, a plurality of metal word linesconfigured to be arranged over the plurality of junction type wordlines, and a plurality of conduction contacts configured to electricallyconnect the plurality of junction type word lines with the plurality ofmetal word lines and to be arranged along every desired cell stringnumber, wherein each of conduction contacts of the plurality ofconduction contacts arranged in each of odd word lines of the pluralityof junction type word lines is arranged between conduction contacts ofthe plurality of conduction contacts arranged in each of even word linesof the plurality of junction type conduction contacts which is adjacentto each of the odd word lines.

Still another example embodiment provides a method for manufacturing aphase change memory device that includes forming a plurality of unitphase change memory cells on a semiconductor substrate which junctionregions are formed therein, forming a plurality of conduction contactsconfigured to be connected to the junction regions every a desired unitphase change memory cell number, and forming a plurality of first wiringlines configured to be connected to the plurality of conductioncontacts, wherein conduction contacts of the plurality of conductioncontacts which are arranged on adjacent first wiring lines areconfigured not to be arranged adjacent to each other in a second wiringline direction.

These and other features, aspects, and embodiments are described belowin the section entitled “Detailed Description.”

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thesubject matter of the present disclosure will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a sectional view of a conventional phase change memory device;

FIG. 2 is a lay out of the conventional phase change memory device inFIG. 1;

FIG. 3 is a lay out of a phase change memory device according to anexample embodiment;

FIG. 4 is a sectional view of the phase change memory device in FIG. 3;and

FIG. 5 is a lay out of a phase change memory device according to anotherexample embodiment.

DETAILED DESCRIPTION

Exemplary embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofexemplary embodiments (and intermediate structures). As such, variationsfrom the shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,exemplary embodiments should not be construed as limited to theparticular shapes of regions illustrated herein but may be to includedeviations in shapes that result, for example, from manufacturing. Inthe drawings, lengths and sizes of layers and regions may be exaggeratedfor clarity. Like reference numerals in the drawings denote likeelements.

FIG. 3 is a lay out of a phase change memory device according to anexample embodiment. Referring to FIG. 3, a plurality of conductioncontacts 221 are arranged between every desired number of unit memorycells in a first wiring line direction. In a second wiring linedirection, each of the conductive contacts 221 is configured not to bearranged adjacent to the conduction contact 221 which is connected toadjacent first wiring line. The conduction contacts 221 are arranged inadjacent first wiring lines are configured not to be arranged adjacentto each other in the second wiring line direction.

Herein, the first wiring lines may be word lines or metal word lines 223and second wiring lines may be bit lines 217. The first and secondwiring lines are orthogonally crossed to each other. The conductioncontacts 221 serve as word line contacts.

For example, as shown in FIG. 3, the word line contacts 221 are arrangedalong every sixteen units of memory cells. Word line contacts 221Aarranged in the first metal word lines 223A are not arranged adjacent tothe word line contacts 221B arranged in the second metal word lines 223Bwhich are arranged adjacent to the first metal word lines 223A in thedirection of the bit line 217. Similarly, word line contacts 221B of theword line contacts 221 arranged in the second metal word lines 223B arenot arranged adjacent to the word line contacts 221C arranged in thethird metal word lines 223C which are arranged adjacent to the secondmetal word lines 223B in the direction of the bit line 217.

Accordingly, a minimum distance D2 between the word line contactsadjacent in the direction of the bit line 170 is ensured by at least thewidth of the metal word line 223 plus the distance D1 of FIG. 2 betweenthe word line contacts in the prior device.

FIG. 4 is a sectional view of the phase change memory device taken alongthe line X1-X2 of FIG. 3. Referring to FIG. 4, a junction region 203serving as a word line is formed in a semiconductor substrate 203.Diodes 207 and phase change material patterns 209 are formed on thejunction region 203 to form unit memory cells. Then, top electrodecontacts 213 and the bit lines 217 being electrically connected the topelectrode contacts 213 are formed on the phase change material patterns209.

Word line contacts 221 on the immediately adjacent metal word lines ofthe metal word lines 223 are configured not to be arranged adjacent toeach other along the bit line direction. Accordingly, in the exampleembodiment, the number of word line contacts are reduced, while thenumber of cell strings 225 between the word line contacts 221 can beincreased.

The reference numeral 205, 215 and 219 designate a first through thirdinterlayer insulating layers. Metal word lines 223 are arranged to beelectrically connected, i.e., coupled, to the word line contacts 221.

For example, in the phase change memory device of the prior art asdepicted in FIG. 1, the word line contacts are arranged along everyeight unit memory cells. However, in the example embodiment, as depictedin FIGS. 3 and 4, the word line contacts are arranged along everysixteen unit memory cells such that the word line contacts which arearranged on the adjacent metal word lines are configured not to bearranged adjacent to each other.

As compared with FIG. 1 and FIG. 4, it is known that a number of wordline contacts are reduced. Depending on reducing the number of word linecontacts, the number of cell strings which can be formed between theword line contacts can be increased, thereby improving the integrity ofthe memory device.

In the example embodiment, the minimal distance separating adjacent wordline contacts in the bit line direction can be sufficiently ensured suchthat the bridge between the word line contacts can be protected against.Furthermore, the diameter of the word line contact can be ensured at themaximum irregardless of an increase in the shrinkage of the device andgap filling in the word line contact hole can be improved.

The high-cost photo and exposure apparatus is required in the process offorming fine contact holes. However, in the example embodiment, sincethe diameter of the word line contact hole can be ensured at a maximum,a low-cost apparatus can be used instead of using a high-cost photo andexposure apparatus. Furthermore, the number of word line contact holescan be reduced such that the cost required in forming the word linecontact hole can be considerably reduced.

In FIGS. 3 and 4, for example, the word line contacts are shown arrangedevery sixteen unit memory cells. However, it is understood herein thatit is not limited thereto and a number of unit memory cells which beformed between the word line contacts in the phase change memory devicecan be modified to the design purpose of the phase change memory device.

FIG. 5 is a lay out of a phase change memory device according to anotherexample embodiment. Referring to FIG. 5, m cell strings are arrangedbetween two word line contacts 221 in the direction of a metal word line223 or the word line direction. It is understood herein that m may beany number in which m is preferably designated as twelve, sixteen,twenty four, thirty two, or more.

Accordingly, one embodiment of the phase change memory device caninclude first wiring lines (e.g., word lines 223) arranged substantiallyin parallel to each other such that the first wiring lines (e.g., wordlines 223) are grouped into odd numbered first wiring lines (e.g., 223A,223C, and 223E) and grouped into even numbered first wiring lines (e.g.,223B, 223D, and 223F). The phase change memory device can have secondwiring lines (e.g., bit lines 217). The phase change memory device canhave memory cells (e.g., diodes 207 coupled to phase change materialpatterns 209) such that the memory cells are coupled together the firstand second wiring lines (e.g., 223, 217). The phase change memory devicecan also have conduction contacts (e.g., word line contacts 221) coupledto the first wiring lines (e.g., word lines 223). Only one conductioncontact (e.g., word line contacts 221) is coupled to a center of acorresponding odd numbered first wiring line (e.g., any one of 223A,223C, and 223E). Only two corresponding conduction contacts (e.g., wordline contacts 221) are coupled to opposing edges of a corresponding evennumbered row first wiring line (e.g., any one of 223B, 223D, and 223F).The conduction contacts (e.g., word line contacts 221) are arranged onthe first wiring lines (e.g., word lines 223) so that conductioncontacts (e.g., word line contacts 221) are not adjacent to each otherwith respect to immediately adjacent first wiring lines (e.g., wordlines 223). The more cell strings between two adjacent word linecontacts increase, the more highly integrated the memory device can be.

According to a phase change memory device and a manufacturing methodthereof, the distance between adjacent word line contacts can besufficiently ensured such that the bridge between word line contacts canbe prevented and the contact misalignment margin can be ensured.Furthermore, irregardless of an increase in the downsizing ratio ofdevice, the diameter of the word line contact hole can be sufficientlyensured as well as the process step for forming the word line contacthole can be reduced such that the low-cost photo and exposure apparatuscan be used in forming the word line contact hole and the productioncost can be reduced.

While certain embodiments have been described above, it will beunderstood that the embodiments described are by way of example only.Accordingly, the devices and methods described herein should not belimited based on the described embodiments. Rather, the systems andmethods described herein should only be limited in light of the claimsthat follow when taken in conjunction with the above description andaccompanying drawings.

What is claimed is:
 1. A phase change memory device, comprising: aplurality of first wiring lines arranged substantially in parallel toeach other such that the first wiring lines are grouped into odd andeven numbered first wiring lines; a plurality of second wiring lines; aplurality of memory cells coupled to the first and second wiring lines;and a plurality of conduction contacts coupled to the first wiringlines, wherein only one conduction contact is coupled to a center of acorresponding odd numbered first wiring line, wherein only twocorresponding conduction contacts are coupled to opposing edges of acorresponding even numbered first wiring line, wherein the conductioncontacts are arranged on the first wiring lines so that conductioncontacts are not adjacent to each other with respect to immediatelyadjacent first wiring lines.
 2. The phase change memory device of claim1, wherein the first wiring lines are arranged substantiallyorthogonally with respect to the second wiring lines.
 3. The phasechange memory device of claim 1, wherein the first wiring lines are wordlines.
 4. The phase change memory device of claim 3, the second wiringlines are bit lines.
 5. The phase change memory device of claim 1,wherein each memory cell comprises a phase change material patterncoupled to a diode.
 6. The phase change memory device of claim 1,wherein the memory cells are grouped into cell strings.
 7. The phasechange memory device of claim 6, wherein each cell string has m numberof memory cells.
 8. The phase change memory device of claim 6, whereinthe one conduction contact coupled to the center of the correspondingodd numbered first wiring line is positioned between a pair of cellstrings.
 9. The phase change memory device of claim 6, wherein two cellstrings along the corresponding even numbered first wiring line arebetween the two corresponding conduction contacts.
 10. The phase changememory device of claim 1 further comprising a plurality of third wiringlines arranged in parallel to each other and positioned underneath thefirst wiring lines.
 11. The phase change memory device of claim 10wherein the third wiring lines are junction word type word lines. 12.The phase change memory device of claim 3 wherein the first wiring linesare metal word lines.
 13. The phase change memory device of claim 1wherein the second wiring lines are coupled to the memory cells.